| The inherent superiority of polyvinyl chloride(PVC)pipe determines that it can supply construction demand in different engineering fields.It is also the largest proportion of pipe plastics in the plastic supply market.However,for unplasticized polyvinyl chloride(PVC-U)pipe,its circumferential strength is insufficient because of the influence of uniaxial tension process.Increasing wall thickness is a good way to improve strength,but it will lead to an increase in the production of PVC pipe materials and bring other new problems.By analyzing the existing PVC modified materials,physical self-reinforced biaxially oriented polyvinyl chloride(PVC-O)pipe has more development potential and advantages than chemical self-reinforced pipe.Perfecting the expanding forming process of biaxially oriented polyvinyl chloride pipes and putting forward technical improvements are the inevitable demand for the development of PVC materials.The following is the main content of this study:(1)The application status of existing PVC pipes was analyzed,and the reasons for choosing PVC-O pipes were discussed.The technical method of biaxial oriented drawing process suitable for the production of this kind of pipes was introduced.An improved forming process of PVC-O pipes was completed with the partner,and the raw materials,equipment and technological process were provided in detail.(2)Aiming at the biaxial orientation drawing process based on die drawing,the orientation device is improved.The design concept of multi-diameter oriented mould is introduced,and the outer structure of multi-diameter oriented mould is designed according to the main parameters,and two kinds of schemes of structural arrangement are given.The aim is to promote the expansion of tube blank step by step,to improve the reliability and ease of orientation through detailed design.The preparation of PVC-O pipe was completed by multi-diameter oriented mould with running production line.(3)In order to verify the self-reinforcement of the pipe material,the performance parameters of the finished pipe material manufactured by orientation process were compared with those of the traditional non-orientation material with the same formation through the order degree experiment test and material mechanics related experiment test.The results obtained by X-ray diffractometer showed that the atomic arrangement of PVC-O was more orderly than PVC-U.The material mechanics test showed that PVC-O was superior to PVC-U in ring stiffness and ring flexibility.The ring flexibility test and surface crack test show that PVC-O is more difficult to be destroyed than PVC-U.The material mechanics test proves that PVC-O pipe is superior to traditional PVC-U pipe.The test listed in the corresponding chapters shows that the quality of PVC pipe products is improved by advanced process.(4)On the basis of accomplishing the above tasks,the topological optimization design of the multi-diameter oriented mould is further proposed.The internal structure of the expanding mould is redesigned by means of the evolutionary structural optimization.According to the optimization results,an optimum scheme of structural arrangement is selected.The lightweight design is carried out for the inside spider of the scheme of structural arrangement,and the optimum design condition is obtained.The material is removed by 16% and the maximum stress is dropped by 2%.User can export the optimized model for being re-edited. |
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